The present invention is related to a hydrogen dispensing station and a method of operating a hydrogen dispensing station. More particularly, the present invention is directed to a hydrogen dispensing station and method useful for simultaneously dispensing hydrogen gas into at least two receiving vessels.
Because of the interrelationship between the temperature, pressure, and density of gases, the amount of hydrogen, H2, that can safely be introduced into a receiving vessel, such as a vehicle storage tank, during refueling necessarily depends upon factors such as the volume, design pressure, and temperature of the receiving vessel, and the temperature and pressure of the compressed gas inside the tank. Industry convention sets the pressure rating for H2 fuel tanks at the standard temperature of 15 degrees Celsius, so nominal pressure ratings such as 250 bar (25 MPa), 350 bar (35 MPa), 500 bar (50 MPa) and 700 bar (70 MPa), correspond to an internal gas temperature of 15 degrees Celsius.
During rapid refueling of hydrogen, the internal tank temperature will typically rise about 50 degrees Celsius due to adiabatic compression of the gas and the reverse Joule-Thompson effect. After the tank is filled, the temperature and pressure inside the tank will decrease as the gas cools, which may result in a less than complete fill. Wide variations in ambient temperature above or below the standard condition of 15 degrees Celsius can also have a significant effect on the indicated pressure inside the tank during and after refueling.
It is desirable to provide a complete fill. A complete fill is when the receiving vessel contains gas at its target pressure and target temperature after coming to equilibrium with its surroundings.
Since receiving vessels have temperature ratings, it may be desirable to limit the receiving vessel gas temperature during dispensing.
As referred to herein, a gas includes pressurized gas and supercritical fluids. A pressurized gas is a fluid below its critical pressure and below its critical temperature. A supercritical fluid is a fluid above either its critical pressure or its critical temperature.
When hydrogen is to be dispensed into multiple receiving vessels, dispensing may be done by a serial or a parallel approach. A serial approach would entail sequential dispensing to one receiving vessel at a time. A parallel approach would entail simultaneously dispensing to at least two receiving vessels.
Hydrogen dispensing by a serial approach is subject to delays and interruptions if issues arise with either the dispensing station or a receiving vessel. The maximum rate for dispensing to a receiving vessel, while at the same time maximizing the amount of hydrogen dispensed, is limited due to potential temperature rise of the receiving vessel gas temperature during dispensing.
Hydrogen dispensing by a parallel approach generally requires significantly more equipment to facilitate dispensing to multiple receiving vessels at the same time. Dispensing to multiple receiving vessels where the receiving vessels are constructed of different materials and are different sizes may pose additional challenges.